The quantity of fuel injected into the cylinders of internal combustion engines is often used as an input value in connection with a series of emission control strategies. Therefore, it is important to know the exact injected quantity of fuel. If this is known, robust emission control is possible, for example by application of exhaust gas recirculation.
A control device of a management system of the internal combustion engine (engine management system, EMS) usually defines target values for the start and duration of an injection of fuel. The injected quantity is calculated in the EMS for this based on the target values.
The quantity of fuel actually injected can deviate from the target values. A deviation can for example be caused by deposits of combustion residues on the nozzles of the injection devices. Methods for detecting the amount of fuel actually injected are conventionally based on measurement values that are detected by lambda (e.g., oxygen) sensors in the exhaust system and by sensors for air mass flow.
However, the inventors herein have recognized issues with the above approach. As one example, deviations from expected exhaust oxygen concentration may occur due to issues other than fueling errors, such as boost pressure errors. Thus, relying only on the exhaust oxygen sensor output to detect fueling errors may result in unnecessary fueling adjustments when the deviation in exhaust oxygen is due to boost or other issues, reducing engine power or increasing fuel consumption.
Accordingly, embodiments are provided herein to at least partly address the above issues. In one example, a method for controlling an internal combustion engine of a motor vehicle having an induction system, an exhaust system, and an exhaust gas recirculation system, wherein via the exhaust gas recirculation system, a part of an exhaust gas mass flow produced by the internal combustion engine is branched out of the exhaust system, recirculated into an induction plenum chamber of the induction system and passed from there into the internal combustion engine, is provided. The method includes providing an ideal ratio between a component of combusted mass of gas in the induction system (fman) and a concentration of oxides of nitrogen molecules in the exhaust system (CNOx) under a condition that said fman-CNOx ratio correlates with a predetermined known quantity of fuel injected into the internal combustion engine; calculating a target value of a CNOx working point using an fman actual value; providing an actual value of CNOx; comparing the provided actual value and the target value of CNOx; and correcting a present deviation of the actual value of CNOx by adjusting to the corresponding target value by increasing or reducing the quantity of fuel injected.
The method according to the disclosure is thus based on an observation of the concentration of oxides of nitrogen in the exhaust system and of the component of the combusted mass of gas in the induction system, e.g., in the inducted charging air, and, if there is a turbocharger present, in the inducted and compressed charging air. A change in the values indicates a change of the quantity of fuel injected from the predetermined known quantity. A deviation from the corresponding target value may already be detected at a measurement point and the injected amount of fuel may be corrected. With different measurement points, a curve may be determined from the ratio for each measurement point, wherein a deviation of a second curve based on the determined actual values from an ideal curve (the first curve) corresponding to the predetermined quantity of fuel injected corresponds to a deviation of the quantity of fuel injected from the predetermined value. In doing so, a deviation from predetermined values of injected fuel can be detected and corrected during the operation of an internal combustion engine.
In another example, a method includes adjusting an exhaust gas recirculation (EGR) valve position to reach a commanded intake oxygen fraction. Responsive to a measured exhaust NOx concentration differing from an expected exhaust NOx concentration, the method includes adjusting one or more fuel injection parameters. The method further includes, responsive to a measured intake oxygen fraction differing from the commanded intake oxygen fraction, adjusting one or more boost control parameters.
In this way, by comparing expected fractions in the intake and the exhaust at a given EGR rate, fueling errors may be differentiated from boost errors based on whether a deviation in the intake fraction or the exhaust fraction is observed. By doing so, various engine operating parameters, such as fuel injection duration and turbocharger conditions, may be adapted to account for drift in component performance, thus maintaining expected/commanded conditions and efficient engine operation.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.